Antigenic variation of the N. gonorrhoeae pilus is one of the reasons why long term immunity is difficult to achieve, as hosts can get reinfected. Av is dependent on both the RecF-like recombination pathway and the formation of a G4 structure upstream of the pilE promoter, but the exact mechanism is still unknown. The role of G4 structures in the cell is still controversial and understanding how the pilE G4 affects antigenic variation would help G4 structures to be accepted as biologically relevant. The goal of this project is to identify and characterize the proteins that assist in formation, stability, and resolution of the pilE G4 DNA structure in vivo. One of these new proteins could be a potential drug target for preventing recurring gonococcal infections. PUBLIC HEALTH RELEVANCE: By changing their surface pili, the pathogenic bacterium Neisseria gonorrhoeae can infect previously cured hosts. Pilin antigenic variation is a gene conversion event that is dependent on recombination proteins as well as a 16 bp guanine quartet (G4) structure upstream of the expressed pilus gene. The work proposed in this fellowship seeks to establish whether two helicases involved in pilin antigenic variation interact specifically with the G4 structure, and to identify novel G4-binding proteins that play a role in initiating antigenic variation.